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SubjectRe: sata promise and software raid5...
You need to test all the disks running at once, this should give a much
clearer picture of how the system will perform with a raid volume. a
simple test is like so:

-> hdparm -t /dev/sda2 & hdparm -t /dev/sdc2 & hdparm -t /dev/sdc2 &
hdparm -t /dev/sdd2

This will get them all going at once, but may jumble the output a bit.

Evan


On Wed, May 26, 2004 at 03:46:57AM +0400, Andrey Nekrasov wrote:
> Hello,
>
> controller - Promise SATA 150 TX4, linux 2.6.7-rc1-bk1, HDD Maxtor
> 250Gb (x4)
>
> Why so slowly reads (and writes) with software raid5?
>
> gnome:~ # hdparm -t /dev/sda2
>
> /dev/sda2:
> Timing buffered disk reads: 148 MB in 3.01 seconds = 49.16 MB/sec
> gnome:~ # hdparm -t /dev/sdb2
>
> /dev/sdb2:
> Timing buffered disk reads: 148 MB in 3.02 seconds = 49.01 MB/sec
> gnome:~ # hdparm -t /dev/sdc2
>
> /dev/sdc2:
> Timing buffered disk reads: 148 MB in 3.03 seconds = 48.90 MB/sec
> gnome:~ # hdparm -t /dev/sdd2
>
> /dev/sdd2:
> Timing buffered disk reads: 144 MB in 3.00 seconds = 47.96 MB/sec
> gnome:~ #
> gnome:~ #
> gnome:~ # hdparm -t /dev/md0
>
> /dev/md0:
> Timing buffered disk reads: 64 MB in 3.12 seconds = 20.52 MB/sec
> gnome:~ #
>
>
> gnome:~ # cat /etc/raidtab
> raiddev /dev/md0
> raid-level 5
> nr-raid-disks 4
> nr-spare-disks 0
> persistent-superblock 1
> parity-algorithm left-symmetric
> chunk-size 1024
>
> device /dev/sda2
> raid-disk 0
>
> device /dev/sdb2
> raid-disk 1
>
> device /dev/sdc2
> raid-disk 2
>
> device /dev/sdd2
> raid-disk 3
>
>
> bye
> --
>
>
> -
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